#标准读取环境变量的写法应该是$ENV{INCLUDE}，不过写成{INCLUDE}也能够正常工作
FIND_PATH(MAVLINK_INCLUDE_DIR common/mavlink.h
  "{INCLUDE}"
  "{LIB_DIR}/include"
)

IF (MAVLINK_INCLUDE_DIR)
  SET(MAVLINK_FOUND TRUE)
ENDIF()
